Digital imaging displays use individual addressable picture subpixels or pixels to display imagery and data on the displays. These pixels are designed to meet a variety of objectives for a product and for manufacturing processes. For example, pixel layout density, process design rules, interconnect cross-talk, and power distribution are all concerns for imaging displays. The displays are also designed to match the needs of the human visual system.
Typical pixel layouts used in digital imaging displays are shown in FIGS. 2 and 3. Referring to FIG. 2, a prior art stripe pattern of alternating red 10, green 12, and blue 14 light emitting pixel columns are interspersed with non-light emitting areas. A typical design attempts to reduce the amount of non-light emitting area to increase the amount of light that can be emitted from the device. The ratio between the light emitting area and the non-light emitting area is called the fill factor. Referring to FIG. 3, a prior art delta pattern is illustrated in which alternate rows 22 and 24 of the stripes of FIG. 2 are placed out of phase.
Digital imaging displays using the pixel layouts illustrated in FIGS. 2 and 3 can be found in various display technologies. In particular, they may be applied in organic light emitting diode (OLED) displays. OLED displays have many advantages as a flat-panel display device and are useful in optical systems.
It is well known in the art to use fiber-optic subpixels in conjunction with display devices to transport the light from a display to a different location. Conventionally, fiber subpixels or faceplates are placed above the cover of a display, for example an LCD or OLED device. Sakai et al. describe a tiled display application in U.S. Pat. No. 5,465,315, issued Nov. 7, 1995, using fiber arrays in conjunction with LCD displays. However, most fiber subpixels or light pipes have a circular cross-section. This circular cross-section does not match the typical, rectangular shape of pixels causing light loss in coupling from a display to a fiber for applications in which a single fiber or light pipe is associated with pixels or subpixels. In the best case, only 78% of the light from a square pixel enters a circular light fiber centered on, and touching, a square pixel, as shown in FIG. 4. Referring to FIG. 4, a circle 30 is shown superimposed above a square 32 circumscribing it. If the fibers are made larger, so as to cover a greater portion of the area of the pixel (as shown in FIG. 5, which illustrates a square 32 circumscribed by a circle 40), the density of pixels is reduced. Rectangular pixels with larger aspect ratios become progressively worse. The situation is exacerbated when the fill factor of the display is taken into account. Any non-light emitting area located within the fiber area is effectively wasted and increases the cost of the fiber. If the fibers are made very small so that many fibers are associated with every pixel, costs also increase and the fill factor of the device is replicated on the viewing surface. Moreover, fiber plates with many small subpixels are more expensive than arrays of larger plastic light pipes. If single, larger fibers are associated with an entire conventional three-color pixel, the fill factor and light coupling are even more problematic.
JP07028050 entitled “Image Display Device” describes an image displaying device where many dot-shaped pixels are arranged two-dimensionally and a filter consisting of optical fibers is arranged on the display optical path of the image displaying device. It is also known to create hexagonal pixel shapes as described in, for example, JP 7261166 A.
In all of these designs, one or more fibers or light pipes are associated with a single pixel subpixel of one color. Hence, the fiber subpixels associated with each color component of a pixel must be small relative to the pixel size.
There is a need therefore for an improved color display design with improved coupling to an optical fiber faceplate.